Spark plug



L. F. MARTEN SPARK PLUG Filed June 24 1922 LOUIS IF. MARTEN, OF-ST.CHARLES, MISSOURI; LENA J. MARTEN EXECUTRIX OF SAID LOUIS F. MARTJEN,DECEASJED.

SPARK PLUG.

Application filed June 24, 1922. Serial No. 570,659.

To all whom t may concern.'

Be it known that I, Louis F. MARTEN, `a citizen of the United States,and residing at St. Charles, county of St. Charles, Missouri, haveinvented the new and'useful Improvement in Spark Plugs, of which thefollo-Wing is a speciiication'.

This invention relates to spark plugs, such as are used on internalcombustion engines and the like.

@ne of the objects of this invention is to provide 'a spark plug inwhich pitting or corrosion of the electrodes may be obviated.

Anotherv object of this invention is to provide a spark plug in whichthe deposit of carbon on the electrodes may be prevented.

'Further objects will appear from the detail description taken inconnection with the accompanying drawing, which represents a view inelevation of a spark plug embodyin this invention.

tTtezt'erring to the accompanying drawing, 1 represents the body of' theplug which 1s ordinarily constructed of steel and ispro'- vided withthreads 2 for attachment to the cylinder head. Suitably mounted in thebody l is an insulating tube 3 of porcelain Y or other suitable materialand within which is suitably mounteda metal rod 4, the lower end ofwhich is adapted to provide a central electrode 5. The'upper end of therod 4 may be threaded and a suitable thumb nut 6 mounted thereon formaking the necessary electrical connections thereto. All of these partsmay be of any usual well known construction and will, therefore, requireno further description.

The lower end of the body 1 is formed to provide a rim 7 spaced from thecentral electrode 5 and mounted on the rim 7 in any usual manner is anelectrode 8 which may be bent toward the electrode 5 so as to pro-y videa small air gap therebetween.

ln spark plugs as ordinarily constructed, pitting orcorrosion of theelectrodes 5 and 8 takes place in service. This is due to burning of theelectrodes by the heating etiect of the spark and the consequentvformation of oxide on the surface of the electrode. This oxide forms ina layer on the surface and being a poor conductor of electricity,

renders -t e action of the spark plug uncertain. Furthermore theformation `of oxide on the electrode surface renders said surface roughand uneven, a. condition which permits the deposit of carbon thereon.

ln accordance with this invention, the electrodes 5 and 8 andthe rim 7are plated with silver or a similar vmetal having a high heatconductivity and giving a non-oxidizable surface. Gold and copper arealso serviceable to a lesser extent for this purpose, but moresatisfactory results are 4obtained from silver.v Silver not only has ahigh heat conductivity but it does not readily oxidize in the air.Consequently when a spark is made between the electrodes, the heat ofthe spark on the electrode is quickly carried away by conduction through,the silver coating. As a result, the temperature of the electrodes atthe point of formation of the spark is prevented from-rising to a pointwhere oxidationwill take place. Furthermore if Ithe temperature shouldrise, the material of the coating offers a greater resistance tooxidation than other materials.

It will be noted further that in accordance with this invention thecoating 9 isl continuous over the electrode `S'and also the end of theshell 7. This provides a quantity of metal of high conductivity in acontinuous mass and extending from the sparking surface ofthe electrodeover an extended area of the shell. This mass of metal, therefore,provides a sort of heat reservoir into which the heat liberated at theelectrode may flow. The heat thus liberated is quick] carried away fromthe electrode so as to keep the same from getting too hot. During theshort interval between applications of heat, the heat so stored in thisreservoir may be transmitted tothe shell by which it ma then be carriedoii for radiation. It will 4be noted further that the metall) makesintimate contact with an eX- tended surface of the .shell 7 Thisprovides a large area of contact and, therefore, contact of highconductivity between the metal 9 and the shell 7 so as to provide for arapid transfer of heat from the former to the latter; It is evident,therefore, that this invention provides means for rapidly leading o'theheat from the sparkin surfaces and delivering the same to the shel forradiation.

The silver coating, therefore, which is indicated at 9 serves not onlyto prevent corrosion of the electrodes, but on account of the fact thatit remains clean and smooth, prevents the deposit of carbon' thereon.

Consequently a spark plug constructed inaccordanc'e with this inventionwill have a longer useful life than that of the ordinary plu It; is`obvious that various changes may be made in details of construct-ionwithout departing from the spirit of this invention; it is, therefore,to be understood that this invention is not to be limited to the specicdetails shown and described.

Having thus described the invention, 'what is claimed is: 1 f

'1. A spark plug, comprising, a central electrode, a shell having anelectrode between which and said central electrode sparking takes place,a non-oxidizing adher- ,ing plating -of high conductivity covering Ithesparking surfaces of said central electrode, and a continuousnon-oxidizing adhering plating of high conductivity covering thesparking surface of said shell elec trode and the end of said shell.

2. A spark plug, comprising, a central electrode, a shell having anelectrode between Which and said central electrode sparkingtakes place,a. plating of non-oxidizing metal covering the sparking surface of saidcentral electrode, and a non-oxidizing metal coating of highconductivity covering said shell and electrode and adapted to provide aheat reservoir for drawing heat from the sparking surface thereof.

3. A spark plug, comprising, a central electrode, a shell having anelectrode between which and 'said central electrode sparking takesplace, a plating of non-oxidizing metal covering the sparking surface ofsaidcentral electrode, and a non-oxidizing metal coating of highconductivity covering the end `of said shell and its electrode i andadapted to provide contact of high conductivity between said coating andsaid.

Louis F. MARTEN.

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